A disorder in type III procollagen appears to be responsible for an autosomal recessively inherited connective tissue disease: Ehlers-Danlos type IV. patients affected by the syndrome have greatly diminished levels of type III or, in some cases, lack the protein entirely. The primary objective of this proposal is to investigate the coordinate expression of type I and type III human procollagen genes in normal cell lines and define molecular characteristics of the Ehlers-Danlos IV syndrome in which thpe III synthesis is absent or reduced. The following experiments will be pursued: (a) cloning of a cDNA encoding for pro alpha 1 (III) sequences; (b) isolation of the pro alpha 1 (III) gene from human genomic libraries; (c) measurement of the relative number of genes for pro alpha 1 (I), pro alpha 2 (I) and pro alpha 1(III) in cell cultures derived from normal fibroblasts, and determination of the chromosomal assignment of the three genes; (d) definition of the nature of the mutations in 40 patients with Ehlers-Danlos type IV by classifying them according to their "molecular" characteristics (e.g., pro alpha 1 (III) gene, present or absent, pro alpha 1 (III) mRNA, functional, unfunctional or absent); (e) cloning, isolation and characterization of the pro alpha 1 (III) gene from patients in which the above analysis suggested a "regulartory mutation."